Thermostat for refrigerating apparatus



June 1933. F. R. BICHOWSKY 1,915,265

THERMOSTAT FOR REFRIGERATING' APPARATUS Filed Dec. 29, 1928 PatentedJune 20, 1933 UNITED STATES PATENT OFFICE I'RANCIS B. BICHOWSKY, OFWASHINGTON, DISTRICT OI COLUMBIA, ASSIGNOR 1'0 FBIGIDAIRE CORPORATION,OF DAYTON, OHIO, A COBTORATIUU OF DELAWARE THEBMOSTAT 1 R BEFBIGERATINGAPPARATUS Application filed December 29,1928. Serial No. 329,111.

This invention relates to refrigerating apparatus and more particularlyto a refrigcrating system wherein the energy source is controlled bymeans of a thermostat having energy being controlled by an element witha flexible chamber receiving, pressures from shown.

a fluid medium of such a character that the medium furnishes suflicientoperatmg pressure at the low temperatures prevailing during theoperation of the system and does not roduce'excessive pressureswhen thesystem 18 temporarily non-operative. Under certain conditions the fluidmedium may be separate from the refrigerant of the system,

Further objects and advantages of the present invention will be apparentfrom thefollowing description, reference being had to the accompanyingdrawing, wherein a preferred form of the invention is clearly In thedrawing The figure is a view partly diagrammatic and partly-in crosssection of a refrigerating system embodying features of this invention.v

A refrigerating system embodying features of this invention may comprisea comressor 2O which delivers compressed re-- rigerant to a condenser21. The condenser 21 delivers condensed refrigerant to a receiver orstorage reservoir 22. From thence the refrigerant may be delivered bymeans of a pipe 23 to an evaporator 24. In the evaporator 24 therefrigerant is evaporated and returns to the compressor 20, preferablythrough a pipe 25 delivering into the'crankcase of the compressor. Inthis particular embodiment, the system may be of the'nexpansion type, inwhich case the liquid refrigerant from the pipe 23 passes to an automatic expansion valve 26 wherein the refrigerant is automaticallyexpanded to a pre-' determined low ressure. The expanded refrigerant mayt en pass through a pipe 27 to the evaporator, for instance to the innercoils 28; The coils 28 may form a freezing zone for the reception oftrays for forming ice cubes and the like. After passing through theinner coils 28 the refrigerant may pass to the outer air cooling coils29 and from thence to the pipe 25 and the compressor 20. If desired, theautomatic'expansion valve 26 may be provided with an artificialatmosphere formed by the tube 30 and the bulb 31 so that the atmosphereon one side of the diaphragm in the expansion valve 26 may be keptsubstantially constant, since the bulb 31 may be placed in the space tobe refrigerated.

The refrigerating system may be intermittently operated, for instance,by being intermittently driven by'la motor 32, which may be connected bythe belt 33 with a flywheel 34 of the compressor 20. The motor 32 may bestarted and stopped by means of a snap switch 35 which is operated by aflexible chamber 36 connected by tubing 37. with a,"

thermostatic bulb 38 placed adjacent to the evaporator 24. A volatilefluid in the bulb 38 actuates the flexible chamber 36, so that it opensand closesthe electric contacts 39 for making and breaking the electriccircuit 40 which supplies energy to the motor 32. This system, as thusfar described, may be, though not necessarily of the ty e described inthe application of llarry B. ull, Serial No.'183,480, filed April 13,1927, now Patsent 1,883,920 granted Oct-25 1932 which is merely referredto as an example of a refrigerating system which may be modified toembody features of this invention. It is obvious, however, that othersystems may embodyfeatures of this invention. The snap .switch may be,though not necessarily, of

vided with the snap mechanism 53 and with 2 the electrical contacts 39.In this articular embodiment, an adjustable pointe screw 54 acts on thecup-shaped end member 55 of a spring 56. The other end of the spring 56may be provided with a cup-shaped member 57 engagin with stationarypointed member 58. As t e end of the arm 50 swings up and down, thealignment of the members 58 and 54 is such that a snap action isproduced by virtue of the compression of the spring 56 and the alignmentof the members 58, 54 causing the spring to reach an intermediate pointvof maximum compression. Other adjustments, such as the spring 60 havingan adjustable connection 61 with thearm 50, together with the adjustment54 enable the snap switch to be so'adjusted that the motor is startedand stopped to produce predetermined high and low pressures in thevicinity of the evaporator 24. i

In domestic refrigerators and the like the predominating temperatures inthe evaporator at present hover around 10 C. (14 F.) Thus 1t is seenthat if the thermostatic bulb 38 should be filled with pure sulphurdioxide, the pressure acting on the flexible chamber 36 would be 0 lbs.gauge. It thus would seem that, at the temperatures when the thermostatshould be most-sensitive, that actually the thermostat is providing theleast a cunt of pressure. Should the thermostati hulb be filled withmethyl chloride, the pressure acting on the flexiblechamber 36 would besufiicient at temperatures around --10 C. (14 F.). However, should thesystem remain idle for a long period of time, as during the vacancy ofthe residence, during transportation of the system, or the like, thetemperatures acting on the bulb 38 might rise to some temperature suchas 40 C. 104 F.). At this temperature, the pure methyl chloride wouldexert a pressure of 112 lbsgauge. Thls 13 such an excessive pressurethat it has a tendency to distort the members of the flexible chamber 36and possibly the knife edge contact of .the member 52which is close tothe fulcrum point 51.

In order to overcome these various objections, fluids may be so chosen,according to this lnvention, that they may be mutually soluble,non-reacting and at least two may be so chosen that one has a pressureabove and the other has a pressure below the pressure necessary tooperate the movable control member at the predominant operatingtemperature of the refrigerating system. Thus amequal mixture of sulphurdioxide and methyl chloride may be made. In a preferred embodiment, theproportions of these substances may be-in the ratio of one mol ofsulphur dioxide to one mol of methyl chloswitch. Should the temperaturerise to 40 0. (104 F.), this mixture would exert only about.90 lbs.gaugeawhich would be insuflicient to distort the mechanism of the typeherein disclosed. Another mixture which is suitable under theseconditions is methyl chloride and nori'nal butane in the proportions oftwo parts of methyl chloride and one part of normal butane. Such amixture has about 5 lbs. gauge pressure at 10 C.

14 and only 60 or lbs. at 40 C. 104 Variousother mixtures in accordancewith the principles herein disclosed may bechosen. Some of the preferredsubstances for making these mixtures are at least two of the following:sulphur dioxide, methyl chloride, isobutane and the pair ammonia andmethylene. In general, it is necessary to obtain at least two mutuallysoluble and non-reacting fluids, or liquids, in which one has thepressure above, and the other a pressure below, that necessary tooperate the movable control member at the predominant operatingtemperature. The exact desired pressure may be obtained by varying theproportions of the substances so mixed.

While the form of embodiment of the in vention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows: 1. In a refrigeration system, controlmeans therefor, said control means comprising a thermostat elementcontaining a mixture of at least two mutually soluble, non-reactingfluids having pressures one above and the other below the pressurenecessary to operate said movable control member at a predominantoperating temperature of the refrigcrating. system.

2. In a refrigeration system, control means therefor, said control meanscomprising a thermostat element containing a mixture of at least twomutually soluble, nomreacting fluids having premures one above and theother below the pressure n v-;-: ry to operate said movable controlmember at the lower operating temperature limit of the refrigeratingsystem.

3. In a refrigeration'system, control means therefor, said control,means comprising -a thermostat element containing a mixture of sulphurdioxide and methyl chloride.

4. In a refrigeration system, control means therefor, said control meanscomprising a thermomat element containing a mixture of sulphur dioxideand methyl chloride in the proportions of one mol of sulphur dioxide andone mol of methyl chloride.

5. In a refrigeration system, control means.

therefor, said control means comprising a thermostat element containinga mixture of at least two mutually soluble, non-reacting fluids havinpressures one above and the other below t e pressure necessary tooperatesaid movable control member at a predominant operating tem rature oftherefrigerating system, said uid medium containing at least two of thefollowing substances, sulphur dioxide, methylchloride, normal butane,isobutane and the pair, ammonia and methylamine.

6. In a thermostatic control means for refrigerating apparatus in whichin order to operate the control means a volatile liquid is used havingan insuflicient vapor pressure at the low operating temperatures toproper- 1y actuate the control means, the method of correcting the'vapor pressure characteristics by adding asecond volatile liquid havinga 'higher vapor pressure in a quantity limited so as to prevent theoccurrence of excessivevapor pressures/at :high temperatures wh theapparatus is idle, but providing an mcreased vaponpressure at operatingtempera tures.

In testimony whereof I hereto aflix my signature.

RANCIS R. BICHOWSKY.

